The PP-90 is an automatic-only weapon that uses the straight blowbackmethod of operation, chambered for the 9×18mm Makarov cartridge. The weapon bears a conceptual resemblance to the 9×19mm FMGsubmachine gun made by the American company Ares. The PP-90 consist of the following main groups: the receiver which houses the barrel, action, safety, fire selector switch and supports the pistol grip with magazine well and the shoulder rest. When carried in the stowed position the pistol grip and magazine are folded under the barrel in line with the bore axis and covered by the folded stock body. The folded weapon resembles a cuboid with the following dimensions – 270 × 90 × 32 mm, devoid of any protruding elements, enabling easy concealment. To ready the weapon for firing the stock is pivoted out, the safety is disengaged and the bolt cocked. The bolt’s cocking handle is placed at the rear end of the receiver housing and is accessed from beneath the stock. During the design phase, emphasis was placed on safety when operating the weapon; the internal mechanisms are configured to ensure that it is impossible to discharge the firearm in its folded position or when the stock is not fully deployed. The PP-90 also has a manual safety and fire selector switch. The safety toggle, installed on the left side of the receiver housing, has two settings: a top “P” position – indicating the weapon is safe and the bottom “O” setting – for automatic fire. The "safe" setting mechanically disables the bolt catch. The weapon’s internal safety mechanism also features a drop safety that prevents it from being discharged when dropped with a loaded chamber. The submachine gun is fed from a detachable 30-round box magazine, placed in a well inside the hollowed pistol grip. The magazine catch is located in the heel of the pistol grip. For aimed firing the PP-90 uses flip-up iron sights ; these are made from thin sheet metal and fold down to lie flush against the receiver housing top cover. The barrel's muzzle is also threaded and will take a sound suppressor. The submachine gun with spare magazines and a cleaning brush is carried in a holster that can be slung from a duty belt or shoulder rig. The weapon can also be used with a sling.
Variants
A version of the PP-90 chambered in the 9×19mm Parabellum pistol cartridge is known as the PP-92.
A selective fire version has also been developed, designated PP-90M.